Sanitization of a surface with light relates to administering doses of light of a certain wavelength or spectrum of wavelengths. The light has an intensity, with the product of intensity and time resulting in a dose. A measure of intensity is Watts/cm2. The dose is typically applied per unit area; a measure of dosage is J/cm2, i.e., the product of Watts/cm2 and time, or Watt-seconds per cm2. The light source has an intensity at the source, typically the surface of the bulb. The intensity of the source at the surface depends on the distance of the light source from the surface and how the light is focused.
Sanitization is a term that refers to making a substantial reduction of bacteria and/or viruses at a surface. A light that provides suitable spectra for killing bacteria or viruses is generally referred to as a germicidal light source.